Expansion connection for fire rated ceiling grid system



Oct. 31, 1967 Filed March 24, 1966 G. C. ADAMS SY TEM 2 Sheets-SheetINVENTOR.

Oct. 31, 1967 c, ADAMS 3,350,125

EXPANSION CONNECTION FOR FIRE RATED CEILING GRID SYSTEM Filed March 24,1966 2 Sheets-Sheet 2 INVENTOR.

// W, pflawgf United States Patent EXPANSION CONNECTION FOR FIRE RATEDCEILING GRID SYSTEM George C. Adams, Ann Arbor, Mich., assignor toRollform, Incorporated, Ann Arbor, Mich., a corporation of MichiganFiled Mar. 24, 1966,'Ser. No. 537,100 1 Claim. (Cl. 287--189.36)

ABSTRACT OF THE DISCLOSURE The instant invention comprises a pair ofmain T-bars or T-members butted end-to-end in a grid system and held inthis position by a splicer which is attached thereto by suitable clipand slot means in a manner permitting controlled expansion of theT-members when exposed to fire or similar conditions and withoutdisrupting the ceiling assembly. To this end, at least one of the mainT-members is provided with a cut-out area in the vertical flange thereofadjacent its butted end and within the portion lapped by the splicer. Inorder to make the T-member adequately strong under normal conditions andat the same time permit it to collapse smoothly and uniformly Withoutdisrupting the ceiling, the cut-out area extends downwardly from theupper edgejof the vertical flange to a point adjacent to but spacedabove the horizontal bottom flanges. This arrangement leaves a narrowportion of the vertical flange between the cut-out area and thehorizontal flanges which serves a stilfening and strengthening functionunder normal service conditions. A single generally V-shaped notchprovided in the narrow vertical flange portion intermediate the oppositesides of the cutout area causes the portion of the T-member below thecut-out area to fold downwardly under thermal expansion conditions withthe apex of the fold at the notch. Movement of the T-member into thecut-out area and relative to the splicer under expansion conditions ispermitted by special clip and elongate slot means interconnecting thesplicer and the vertical flange of the T-bar.. The integrity of the gridassembly in normal service is enhanced by providing the splicer in thearea of the cut-out area with means for attachment of a cross T-member;and, in order to permit elongation of the main T-member under thermalexpansion conditions without opening up the ceiling and withoutinterference from the cross T-member, the attaching means is locatedgenerally in line with the V-notch and disposed at a substantialdistance from the side of the cut-out area remote from the butted endand the remote side of the cut-out area is caused to extend transverselyof the T-member in substantially a straight line from the bottom of thecut-out area.

This invention relates generally to ceiling structures, and particularlyto an improved expansion connection for a suspended ceiling component.

In general, suspended ceilings, of the type to which the presentinvention relates, include a plurality of normally disposedinterconnected grid members suspended from a conventional ceiling oroverhead structure of an enclosure. These grid members conventionallyinclude parallel spaced main grid members which extend one fulldimension of the enclosure and which may be of integral construction butwhich preferably are of end-to-end spliced construction and cross gridmembers which extend normally to and interconnect the main grid members.The main and cross grid members each are of generally inverted T-shapein vertical cross section and together form a latticedefining aplurality of rectangular openings. A rectangular acoustical tile ispositioned in each opening in the lattice and is supported on the bottomflanges of the grid members and provides a generally aestheticallypleasing and acoustically superior ceiling for the enclosure.

One of the problems arising in these ceiling structures relates tomaintaining the integrity thereof under high ambient temperatureconditions. Thus, when a fireoocurs in the enclosure, the metallic gridmembers expand and buckle so that the acoustical tiles in the gridopenings are disturbed and tilted sometimes to such an extent that theyfall through the openings. When this occurs, the elfectiveness of thesuspended ceiling is destroyed and the overhead ceiling and relatedstructure is exposed to the fire so that the latter can spread moreeasily and quickly through the entire structure.

From the foregoing, it is readily apparent that suspended ceilingstructures desirable should maintain their integrity and hold theindividual tiles in place as long as possible under any elevatedtemperature or fire condition. In this manner, fire within the enclosureis delayed and perhaps prevented from spreading to the overheadstructure and therefore to other parts of the building.

The main object of the present invention therefore is to provide animproved grid member assembly for a suspended ceiling structure which isadapted to isolate and control thermal expansion thereof to a particulararea and thereby maintain the integrity of the suspended ceiling underelevated ambient temperature conditions.

Further objects include a grid member assembly of the above characterwhich is relatively inexpensive to manu facture, sturdy in constructionand reliable in use.

Other objects and advantages of the present invention will become moreapparent from a consideration of the following detailed descriptiontaken in conjunction with the drawings in which:

FIGURE 1 is a perspective view illustrating a main grid constructedaccording to the present invention and shown with a pair of cross gridmembers before assembly thereof;

FIG. 2 is a sectional view of FIG. 1 taken along the line 2-2 thereof;and

FIG. 3 is an exploded perspective view of the grid member of FIG. 1.

' Broadly described, the present invention comprises a grid assemblyincluding an elongated grid member of generally inverted T-shapevertical cross section defining a vertical flange and a pair ofhorizontal flanges, said vertical flange having a rectangular slottherein intermediate its ends and extending to an area adjacent saidhorizontal flanges, a generally V-shaped notch in the bottom of saidslot intermediate the ends thereof whereby thermal expansion of saidgrid member causes said slot to collapse and said horizontal flanges tobend downwardly in the area below said slot forming an apex oppositesaid notch.

Referring now more specifically to the drawings, a main grid memberassembly embodying the present invention is illustrated generally at 11in FIG. 1 and is seen to include a grid member 13 commonly referred toin the trade as a T-member because of its generally inverted T-shapedvertical cross section. As shown, the T-member 13 has a vertical flange15 and a pair of horizontal bottom flanges 17, 19 at opposite sides ofthe flange 15. The grid member 13 is shown in aligned and abuttingend-to-end relation with another grid member 21 having a vertical flange23 and horizontal flanges 25, 27 identical to the flanges 15 and 17, 19,respectively, of the grid member 13. The main grid members 13, 21 arereleasably held together by a splicer 29 and permit using a standardlength main grid member, e.g., 12 feet, in various multiples or partsthereof to accommodate different enclosure sizes.

The main grid members are installed in parallel rows spaced apart adistance substantially equal to or slightly greater than one widthdimension of the ceiling panels (not shown) to be used whereby thesepanels rest upon the horizontal flanges 17, 19 and 25, 27. The rows ofmain grid members are interconnected by cross grid members 31, 33 whichalso are generally inverted T-shaped in vertical cross section definedby a vertical flange 35, 37 and horizontal flanges 39, 41 and 43, 45,respectively. The extremities of the cross grids 31, 33 are formed withtabs 47, 49 receivable in a set of apertures 51, 53 formed in thevertical flange 15 of the main grid 13. Additional sets of apertures areformed in the main grid vertical flange 15 (not shown), the splicer 29as at 50, 52 and the main grid vertical flange 23 as at 54, 56 toreceive projecting tabs on other cross grids (not shown) and these setsof apertures are spaced apart a distance substantially equal to orslightly greater than the other width dimension of the ceiling panels(not shown) which are supported thereon so that the grid system formedby the main grids and the cross grids defines substantially arectangular lattice and together with the panels supported thereonpresent an aesthetically pleasing and acoustically superior ceiling forthe enclosure. The details of the interlocking relation between the maingrids and the cross grids do not form a part of the present inventionand are not described further here. Reference, however, may be made tomy copending application Ser. No. 537,055, filed Mar. 24, 1966, for adetailed explanation thereof as well as for an illustration andexplanation of the grid system formed thereby.

As described briefly above, a fire within the enclosure in which theceiling is suspended heats the grid members and causes them to expand.If these grid members are rigidly confined, this expansion causes atleast some of the grid members to buckle whereupon the ceiling panelssupported thereby are either raised, tilted or fall out of the gridsystem and the fire is permitted to spread quickly to the overheadstructure. In an effort to maintain the integrity of the grid system,means may be provided whereby the cross grid members 31, 33 arepermitted to expand without buckling or causing the main grid members tobuckle. One such means is that illustrated in FIG. 1 and illustrated anddescribed in detail in my copending application, Ser. No. 537,055, filedMar. 24, 1966. In addition to the cross grid members, the main gridmembers 13, 21 and therefore the grid assembly 11 also expand under thisheat. Because of the relatively great length of the grid assembly 11,expansion thereof, if left uncontrolled, causes the main grid assemblyto buckle and dislodge the ceiling tile and thereby speeds the spread ofthe fire.

It has been discovered that if a particular area or areas of the maingrid member assembly 11 be weakened in a novel manner, expansion thereofcan be confined to this area or areas and integrity of the system can bemaintained. To this end, the main grid member 13 is seen to have agenerally rectangular cut-out area or slot 55 formed in the verticalflange 15. The cut-out area 55 opens through the upper edge of theflange 15 and extends downwardly therefrom to a point adjacent to butspaced above the horizontal flanges 17, 19 leaving a relatively narrowportion 57 of the vertical flange 15 which serves a strengthening andstiffening function in the normal use of the T-member 13. A generallyV-shaped notch 59 is formed in the narrow flange portion 57 atsubstantially the midpoint thereof. The purpose of the notch 59 is toweaken the flange portion 57 sufficiently so that the lower portion ofthe T-mernber 13 will fold at this point under forces of compression dueto expansion of the member in the event of fire or the like. To thisend, the notch 59 need not extend all the way to the horizontal flanges17 and 19 although it may do so if the loss of strength and stiffnessresulting therefrom is not critical.

When the main grid member 13 is he e a d caused to expand, it collapsesfirst at the area of the slot 55 since this portion of the grid member13 is substantially weaker than the rest of the grid member. Inaddition, because of the notch 59, the flange portion 57 and the flanges17, 19 bend in a fashion forming an apex at the notch 59, substantiallyas shown in dot-dash lines in FIG. 1. The bending of the flange portion57 and the flanges 17, 19 is prevented from occurring in a lateraldirection both by the relatively great strength of the flanges 17, 19 inthis direction and because of the presence of the ceiling panels (notshown) which rest thereon. Further, this bending is prevented fromoccurring upwardly by the presence of the splicer 29, in a manner to bedescribed, and is caused to occur in a vertical downward directionsubstantially as shown in the figure. In this way, the adjacent panel orpanels seated thereon are not lifted therefrom and tend to remain inplace so that the integrity of the ceiling is maintained.

It has been discovered that by utilizing a generally elongate slot 55and by providing only one notch 59 which is disposed centrally of thebottom flange portion 57, the overall force required to bend thehorizontal flanges 17, 19 and the flange portion 57 and thereforecollapse of the T-member 13 at the slot 55 is substantially less than ifa plurality of notches 59 are provided. Tests have demonstratedparticularly that significantly less force is required to start thebending and collapsing action which occurs at the slot 55 when themember 13 is under compression of a magnitude developed in case of afire for example. Apparently, under these conditions, the forces ofcompression are concentrated at the single notch 59 in such a way thatcollapsing begins to occur sooner than if a plurality of notches areused according to conventional practice even though some tearing of themetal at the corners of the notch must occur in order for the bendingaction to progress. The single notch 59, when located as shown anddescribed, concentrates the forces of compression in the T-member 13 insuch a way that bending always occurs first at the notch. The portion ofthe member 13 below the notch 55 begins to fold downwardly into a V-formas shown by broken lines in FIG. 1, and it continues to collapse in thismanner as long as the forces of compression continue to build up in themember. Thus, the single notch 59 provides a construction that isdesirably normally stronger and more rigid than a similar constructionhaving more than one notch but unexpectedly yields more readily toinitial bending. This assures a more effective control of the collapsingaction under fire conditions and maintains the integrity of the ceilingfor a longer time than otherwise would be the case.

As shown in FIGS. 1 and 3, the splicer 29 is substantially S-shaped invertical cross section and includes a vertical web 61 adapted to overliethe vertical flange 15 of the main grid 13 and a lower horizontal flange63 which seats against the horizontal flange 19. The splicer 29 issecured to the main grid members 13, 21 by butterfly type clips 65, 67,69, 71, 73 which are receivable in key-shaped openings 75, 77, 79 in thevertical flange 15 and key-shaped openings 81, 83 in the vertical flange23. Conveniently, the butterfly clips 65, 67, 69, 71, 73 are struck outfrom the splicer web 61 and are formed by a punching operation duringformation of the splicer 29.

The key slots 75, 77, 79 in the vertical web 15 are oriented oppositelywith respect to the key slots 81, 83 in the vertical web 23 to permiteasy assembly of the parts. Thus, after the splicer 29 is mounted on themain grid 13 with the clips 65, 67, 69 in place in the key slots 75, 77,79, the main grid 21 is brought to position the clips 71, 73 in theslots 81, 83. The clips 65, 67, 69, 71, 73 and the slots 75, 77, 79, 81,83 are of course positioned so that when the main grids 13, 21 are inend-to-end abutting relation, the clips and slots obtain as shown inFIG. 1.

In accordance with the present invention, the slot 55 is positionedbetween two of the key slots 75, 77, 79 and adjacent one end of the maingrid 13. In addition, the key slots 75, 77 on one side of the slot 55are considerably longer than the key slot 79 on the other side of theslot 55. The key slots 81, 83 in the main grid vertical flange 23 aresubstantially the same size as the key slots 79 so that when the partsare assembled as shown in FIG. 1, the clips 69, 71, 73 are precludedfrom further longitudinal movement in their key slots 79, 81, 83 whilethe clips 65, 67 and their slots 75, 77 can move longitudinally relativeto each other. Thus, when the main grid 13 thermally expands, theabutting ends of the main grid members 13, 21 are held intact while theslot 55 collapses and the vertical flange portion 57 and the horizontalflanges 17, 19 bend as shown in dot-dash lines in FIG. 1. During thistime, the clips 65, 67 and their slots 75, 77 slide longitudinallyrelative to each other. It will be understood that the other end (notshown) of the main grid member 21 can be formed similarly to theillustrated end of the main grid 13 to control and confine expansionthereof.

In addition to holding the main grids 13, 21 together, the splicer 29controls the direction of bending of the vertical flange portion 57 andthe horizontal flanges 17, 19. As shown, the splicer flange 63 seatsagainst the grid horizontal flange 19 so that during heat expansion ofthe main grid 13, the flange 19 cannot bend upwardly. As described, theceiling panels (not shown) which are in place in the grid system preventlateral bending thereof so that bending must take place in a downwarddirection as shown by the dot-dash lines in FIG. 1. In this way, thesupported ceiling panels can remain in place in the grid system for alonger time, sincedownward bending of the horizontal flanges 17, 19 willnot unseat them, and a fire in the enclosure will be less apt to spreadto the overhead structure. Also, where the main grids 13, 21 are usedalong one side edge of a ceiling so that ceiling panels are in placeonly on one of the horizontal flanges such as the flange 17, the splicerweb 61 lends support to the main grid 13 on the other side and preventslateral bending thereof.

During heating of the main grid members 13, 21, as during a fire, forexample, some elongation occurs along substantially the entire lengththereof. To accommodate this, the tabs 47, 49 on the cross grid members31, 33 are relatively flexible so that they can bend laterally withelongation of the main grid members 13, 21 and hold the ceiling panelssupported thereon in place. Flexibility of the tabs 47, 49 can beenhanced by cutting a slot 85 in the vertical webs 35, 37 of the crossgrids 31, 33. In any event, unit elongation of the main grids 13, 21between cross grids 31, 33 is not so great as to pose a serious problemand the flexibility of the tabs 47, 49 is sufiicient to maintainintegrity of the system during a fire.

It will' be seen that by the present invention there is provided animproved grid member assembly for a ceiling grid system which controlsand confines heat elongation thereof to a particular area thereof andwhile a preferred embodiment of the present invention has beenillustrated and described above in detail, various additions,substitutions, modifications and omissions may be made thereto withoutdeparting from the spirit of the invention as encompassed by theappended claim.

What is claimed is: A control expansion grid member assembly comprisinga pair of main T-members butted end-to-end and each having a verticalflange and horizontal bottom flanges, one of said T-members beingprovided in its vertical flange and adjacent the butted end thereof witha cut-out area which extends downwardly from the upper edge of theflange to a point adjacent to said horizontal flanges, the bottom ofsaid cutout area being spaced above said horizontal flanges to define arelatively narrow portion of said vertical flange between the bottom ofthe cut-out portion and said horizontal flanges which serves astrengthening and stiffening function, said relatively narrow verticalflange portion having a generally V-shaped notch therein intermediatethe sides of said cut-out area, whereby thermal expansion of saidT-member causes the portion thereof below said cut-out area to folddownwardly in a V-shape with the apex of the fold at said notch, asplicer bridging the joint between said main T-members and extendingacross said cut-out area, and clip and slot means fastening said splicerto the vertical flanges of said T-members, certain of said clip and slotmeans being at the side of said cut-out area remote from the butted endof said one T-member and the slot portions of said certain clip and slotmeans extending from the clip portions thereof in a direction away fromsaid cutout area to permit said one T-member to move relative to saidsplicer and into said cut-out area under thermal expansion conditions,the portion of said splicer extending across said cut-out area beingprovided with means for attachment of a cross T-member the remote sideof said cut-out area extending transversely of the T-member insubstantially a straight line from the bottom of said area and saidcross T-member attachment means being located generally in-line withsaid V-notch and disposed a substantial distance from said remote sideof said cut-out area.

References Cited UNITED STATES PATENTS EDWARD C. ALLEN, PrimaryExaminer.

